Nightcrawler is one of my personal favs in marvel, so naturally in this game i had to have him (after iron fist, dr strange, colossus and war machine) but i was unhappy with his performance, even at lvl 6 due to how quick he dies, although his ability to get past bruisers with protect abilities was quite useful early on, but i focused his iso 8's on his health, defense and attack.
At lvl 9 however, I began to cherish him dearly, his 4th move, Triple threat became highly usefull in taking down Tacticians, especially with a Tactical strike, allowing him to make the opponent dizy with his first attack, then following up with Tripple threat, which also landed his follow up ambush after the initial three hits of Tripple threat, combined with it's high crits (not sure if it applies to the follow up, but his accuracy lets him crit alot anyway), usually topples most tacticians in those total 5 hits. Plus it looks look in action.
So essentianlly his Tripple threat has a 2nd meaning other than initial thre hits as it can potentially be used in a three different move strike.
His Shadow guard comes in useful if a round contains a scrapper and you want to prevent him being hit, and works well if his reflexes are triggered by attacking/ being attacked by a tactician, so overall i thing if given patience to reach him to level 9, his true potential becomes apparent, and as such he does not deserve the negativity he gets.